1. Field of the Invention
The present invention relates to a method and apparatus for performing processing such as resist film formation for a semiconductor substrate, an LCD (Liquid Crystal Device) substrate, or the like.
2. Description of the Related Art
The steps in manufacturing a semiconductor device include a series of steps in which a compressed circuit pattern or the like is transferred by using a photolithography technique to a photoresist film formed on a semiconductor substrate or an LCD substrate, and the transferred circuit pattern is subjected to development processing. The series of steps is performed in a system obtained by combining a coating-development apparatus mainly including a section for coating a resist liquid on a semiconductor wafer (to be referred to as a wafer hereinafter), a section for drying the coated resist liquid, and a section for developing the resist film which is exposed, and an exposure apparatus for performing exposure processing for the resist film.
In a system shown in FIG. 1, a wafer is subjected to draining processing in an adhesion processing unit 11 in a coating development apparatus 1A and then cooled in a cooling unit 12. Thereafter, a coating film (resist film) is coated and formed on the wafer in a coating processing unit 13. After the wafer is subjected to baking processing in a heating unit 14, the wafer is exposed in an exposure apparatus 1B to form a predetermined pattern, and this pattern is developed in a development processing unit 15 in the coating development apparatus 1A. Note that reference numeral 16 denotes a main arm for conveying a wafer to each processing unit, and reference numeral 17 denotes an interface for exchanging a wafer between the coating development apparatus 1A and the exposure apparatus 1B.
The coating processing unit 13 comprises a coating mechanism for coating a resist liquid on the surface of a wafer by, e.g., a spin coating method, and a rinse mechanism for removing a coating film on the peripheral portion, on both the wafer surfaces, of the coating film coated and formed by the coating mechanism, with a rinse liquid, e.g., thinner. In recent years, an exposure processing time in the exposure apparatus 1B has been shortened, and a high-speed exposure apparatus having, e.g., a tact time (processing time for one wafer) of about 30 seconds has been developed. Therefore, the coating film formation processing, in the coating processing unit 13, serving as the pre-processing of the exposure processing must be performed within the tact time of the exposure apparatus. When the coating film formation processing is performed for a time longer than the tact time of the exposure apparatus, the wafer is set in a standby state on the exposure apparatus side to perform the coating film formation processing. As a result, the throughput of the entire system is not increased.
In the coating processing unit 13, after the resist liquid is coated by, e.g., the spin coating method, the resist film is dried while the wafer is rotated. Thereafter, rinse processing, which is called back rinse processing, side rinse processing, or the like, is performed to the resist film on the peripheral portion of both the wafer surfaces. The rinse processing is performed as described above for the following reason. That is, although the thickness of the resist film immediately after the coating processing is uniform on the entire surface of the wafer, the resist liquid increases in thickness by surface tension such that the resist liquid rises up on the wafer peripheral portion. In addition, the resist liquid extends to the peripheral portion of the lower surface of the wafer to form an unnecessary film. In this manner, when the ununiform thick film is formed on the peripheral portion of the wafer, the thick portion of the resist film remains to be completely removed. When the resist film remains as described above, the remaining resist film is peeled in the step of conveying the wafer to generate particles. Note that the reason why the resist film is dried before the rinse processing is that, when the rinse processing is performed before the resist film is not dried to remove the resist film, the resist film becomes loose near the portion where the resist film is removed, and the loose resist film forms particles in the subsequent steps as in the above description.
As described above, in the coating processing unit, since coating processing, drying processing, and rinse processing are performed, there is a limit to shortening of a tact time. For this reason, in order to correspond to the shortening of the tact time of the exposure apparatus, a plurality of coating processing units 13, e.g., two coating processing units 13, are arranged, and the coating processing units 13 must parallel perform coating formation processing as shown in FIG. 2.
In this case, the type of a resist liquid is changed depending on the line width of a pattern to be exposed, in the coating processing unit 13, a resist liquid supply system is generally prepared to coat various types of resist liquids. For example, in order to coat four types of resist liquids, four supply systems each constituted by a vessel for storing a resist liquid, a pipe, a supply pump, a filter, a valve, or the like must be prepared. When the two coating processing units 13 are arranged as described above, eight supply systems are required to coat four types of resist liquids. In fact, since the number of types of resist liquids is considerably large, a large number of instruments related to the resist liquid supply systems are used in a method in which the two coating processing units 13 parallel perform the processing. For this reason, a large space is required, and the cost increases. Although the coating development apparatus is incorporated in a clean room, the clean room has an air cleaner and a floor having a special structure, and the cost per unit area is very expensive. For this reason, it is considerably disadvantageous that two coating processing units are arranged.
In a spin coating method, a resist liquid is dropped on the central portion of a wafer rotated on a spin chuck, and the resist liquid is diffused toward the peripheral portion of the wafer by centrifugal force. In the coating of the resist liquid performed as described above, at present, several types of resist liquids having different viscosities are selectively used in accordance with the line width or the like of a circuit pattern. Conventionally, a plurality of resist liquid storage tanks for storing different types of resist liquids and a plurality of resist liquid supply nozzles for dropping (supplying) each resist liquid on the wafer surface are connected to each other through supply pipes, and each pump connected to each supply pipe is operated by an actuator arranged in the corresponding pump to supply the resist liquid.
However, in the conventional resist coating apparatus of this type, each supply pipe has a pump for supplying a resist liquid and an actuator, arranged in a pump, for controlling the operation of the pump. For this reason, the pipe portion is complicated, a large space is required for the large number of pipes, and the size of the apparatus is disadvantageously increased as a whole. In addition, since each actuator requires equipment such as a sensor and an encoder, the cost increases.